Effect of Si addition on the oxidation resistance of Co–Re–Cr-alloys: Recent attainments in the development of novel alloys

Abstract The influence of silicon on the oxidation behaviour of Co—Re—Cr-alloys has been studied at 1 000°C and 1 100°C. Consideration was given to the synergetic effects between chromium and silicon with respect to the development of a protective Cr2O3 layer. The Si addition to the Co—Re-alloys produces a significant decrease in the evaporation rate of Re oxides. Moreover, the beneficial influence in the transient oxidation period results in a rapid formation of Cr2O3 scale. While the addition of 1 and 2 at.% Si to the ternary Co-17Re-23Cr alloy was insufficient to form a continuous Cr2O3 scale, the addition of 3 at.% silicon caused a change in the oxidation mode resulting in the formation of a nearly continuous Cr2O3 scale. On the oxide/alloy interface of the alloy Co-17Re-30Cr-2Si, a continuous and dense Cr2O3 scale was observed, which remained stable after 100 h exposure protecting the metallic substrate.